Stoichiometric and Catalytic C−C and C−H Bond Formation with B(C6F5)3 via Cationic Intermediates. Issue 39 (18th August 2017)

• Record Type: Journal Article
• Authors: Soltani, Yashar; Wilkins, Lewis C.; Melen, Rebecca L.
• Is Part Of: Angewandte Chemie international edition. Volume 56:Issue 39(2017)
• Page Start: 11995
• Page End: 11999
• Publication Date: 2017-08-18
• Subjects: boron -- cyclization -- homogeneous catalysis -- Lewis acids -- tris(pentafluorophenyl)borane; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201704789
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: This work showcases a new catalytic cyclization reaction using a highly Lewis acidic borane with concomitant C−H or C−C bond formation. The activation of alkyne‐containing substrates with B(C6 F5 )3 enabled the first catalytic intramolecular cyclizations of carboxylic acid substrates using this Lewis acid. In addition, intramolecular cyclizations of esters enable C−C bond formation as catalytic B(C6 F5 )3 can be used to effect formal 1, 5‐alkyl migrations from the ester functional groups to unsaturated carbon–carbon frameworks. This metal‐free method was used for the catalytic formation of complex dihydropyrones and isocoumarins in very good yields under relatively mild conditions with excellent atom efficiency. Abstract : The Lewis acidic borane B(C6 F5 )3 activates alkynes towards an intramolecular cyclization with carboxylic acids. Analogous intramolecular cyclizations of esters via C−C bond formation proceed in good to excellent yields in the presence of catalytic amounts of B(C6 F5 )3 . This process involves a 1, 5‐alkyl migration from the ester functional group to the unsaturated carbon framework.